280 REVISION OF THE MONAXONID SPONGES, i., 



without a proper examination of its surface-features having been 

 made; but if the specimen, from which it was taken, exhibits the 

 characteristic dermal reticulation that would prove it to be also 

 a form of Donatia phiUipensis, then I would be inclined to say 

 that a separation of these forms, as distinct varieties, is not 

 feasible. 



The specimen referred to in the opening paragraph, which I do 

 not consider to belong to D. phiUipensis, differs from the type- 

 specimens of that species chiefly in the absence of a dermal 

 reticulation and of subdermal clefts in the cortex, and in almost 

 all respects is closely similar to D. ingalli var. Icevis. In it, 

 however, just as in D. phiUipensis, spherasters are abundant in 

 the choanosome and spheres are present. Concerning its mega- 

 scleres, exactly the same remarks apply as to those of D. phiUip- 

 ensis, excepting that the largest attain a length of 1670 /x. The 

 spherasters have from 9 to 13 countable rays, the length of which 

 is less than the diameter of the centrum, and which rarely (if 

 ever) exhibit any tendency to branch. Spherasters with one or 

 more rays completely aborted were not observed. The tyl asters 

 are rarely more than 16*5 /x in total diameter, and their rays, 

 which are shorter than the diameter of the centrum, have well- 

 developed terminal knobs densely covered with minute spines; 

 an extremely few, however, ranging in diameter from about 16 

 up to about 23 /x in diameter, have the rays less markedly 

 knobbed, and provided with spines for some distance along their 

 length. The oxyasters, which are abundant, occasionally attain 

 to 43 fi in diameter, and have, as a rule, stout rays (2 to 4 /a in 

 diameter at the base), the distal half of the length of which is 

 covered with well-developed tubercles; some of the more slender- 

 rayed spicules (? developmental forms), however, are without 

 tubercles; in a small proportion of cases, the rays, which in such 

 instances are usually stunted, are provided along their whole 

 length with tubercles, and the spicule then often closely ap- 

 proaches in form to the oxyasters of D. ingaUi as figured by 

 Bowerbank (3, PI. v., fig, 17). In no other example of Donatia 

 examined by me, does the tuberculation of the rays of the oxy- 

 asters reach quite such a degree of development. 



